FOREIGN OBJECT DETECTION WITH SURFEL MAPS

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for detecting foreign objects using a surfel map. One of the methods includes receiving sensor data representing reflection characteristics of electromagnetic waves in an operating environment of an autonomous vehicle. A surfel map representing a portion of the operating environment of the autonomous vehicle is used to determine that the reflection data includes one or more mismatched reflection characteristics for a particular surfel in the surfel map. In response, a foreign object is detected at a location corresponding to the particular surfel having the one or more mismatched reflection characteristics.